There should be no more hops than 7 from the root bridge. If you have a ring topology, the furthest switch is 5 hops away is both directions.
I made a sketch to make it easier to understand. R is the root bridge, the orange line represents the blocked link. Obviously, the numbers are the number of hops.
![](http://supportforums.cisco.com/sites/default/files/legacy/1/7/7/126771-ring_stp.png)
If you had 16 switches in your ring, you would encounter problems.